1. Field of the Invention
The present invention relates to an image forming apparatus of pressure developping type.
2. Description of the Related Art
As one of varuous kinds of image forming apparatus, there is an image forming apparatus of pressure developping type, using a photo-receiving media sheet, such as a photosensitive and pressure sensitive sheet, and an image receiver sheet for pressure developping.
Such a media sheet is coated with microcapsules. The microcapsule contains photohardening material and image forming material in its shell. The receiver sheet is coated with a developping material which reacts with the image forming material in the microcapsules of the media sheet and coloring the receiver sheet.
In such an image forming apparatus of pressure developping type, the operational principle is as following.
When the media sheet, on which a latent image i.e. a selective photo-hardened image is formed by exposure of an original image, and the receiver sheet is superposed on each other and applied with pressure by pressure rollers, the unhardened microcapsules are ruptured. Then the image forming material is flown out therefrom, then reacts with the developping material on the receiver sheet and color-develops the receiver sheet, resulting in forming a desirable image on the receiver sheet.
The media sheet is accommodated in a cartridge in a rolled form in order to prevent the light exposure and prevent the microcapsules from rupturing. The cartridge is mounted to the main body of the image forming apparatus.
The receiver sheet in a cut sheet form is accommodated in a sheet receiver supplying cassette, and is supplied one by one by a sheet supplying device of absorbing type so as not to scratch the coated surface thereof.
The receiver sheet is transported to a resist roller etc. and stopped once there. Then, the receiver sheet is transported from the resist roller etc. to the pressure rollers with a proper timing respect to the tip of the latent image formed portion of the media sheet.
As described above, the image forming apparatus of pressure developping type has a characteristic of a small size and simple structure apparatus since it does not require a photosensitive dram or the developping device which are required in other types of the image forming apparatus.
Accordingly, simplification and miniaturization of the apparatus is desirable and important subject in this type of image forming apparatus so as to make a good use of this characteristic.
However, in the above mentioned kind of the image forming apparatus, since the receiver sheet is stopped once before the pressure rollers in order to obtain the proper timing respect to the tip of the latent image formed portion of the media sheet, a device such as the resist roller etc., is disposed along the relatively short path of the receiver sheet, and the construction of devices such as sensors etc. for enabling the poroper timing is rather complicated, resulting in an increased number of the total components and a difficulty in the miniaturization, the simplification and the cost down of the apparatus.